Embodiments of the present disclosure relate generally to semiconductor devices and methods of manufacturing semiconductor devices, and more particularly to semiconductor devices and methods having a bi-layer, high-k dielectric.
Gate electrodes affect the performance of a semiconductor device. As the gate dielectric layer thickness is reduced, the drive current can be increased, increasing the device performance. However, as the gate dielectric layer becomes thinner, gate leakage is induced, increasing power consumption and reducing device performance. Metal gate electrodes have been used to reduce the effective thickness of the gate dielectric layer and to reduce gate leakage. However, semiconductor devices utilizing metal gates have suffered from such problems as high leakage currents, poly depletion, slower switching speeds, and higher effective work functions. Although the existing devices and methods have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.